PROCESSING OF ENDOPLASMIC-RETICULUM LUMINAL ANTIGENS ASSOCIATED WITH HALOTHANE HEPATITIS IN RAT HEPATOCYTES

In this study we have investigated the mechanism of the processing of trifluoroacetylated liver microsomal protein antigens associated with halothane hepatitis to learn how the immune system might come in conta ct with these proteins to form antibodies directed against them, Rats were treated with halothane and parenchymal (PC) and non-parenchymal c ells (NPC) were isolated 16 hours later, Immunoblotting of the cell ly sates with antisera directed against the trifluoroacetyl hapten showed the presence of high levels of trifluoroacetylated proteins in parenc hymal cells, whereas none of these proteins were detected in endotheli al or Kupffer cells that were isolated by centrifugal elutriation, The half-lives of 100-, 82-, 80-, 63-, 59-, 58-, and 57-kd trifluoroacety lated and native carrier proteins of the trifluoroacetyl hapten in cul tures of rat primary parenchymal. cells were approximately 1 day, The turnovers of all of these trifluoroacetylated proteins, except for tha t of the trifluoroacetylated 100-kd protein, were inhibited by treatme nt of the cells with ammonium chloride, leupeptin, 4-(2-aminoethyl)-be nzenesulfonyl fluoride, or 3-methyladenine (3-RMA). These results indi cate that, in liver, the major source of the formation of trifluoroace tylated antigens associated with halothane hepatitis is the parenchyma l cells, It appears that most of the trifluoroacetylated antigens and possibly the native carrier protein of the trifluoroacetyl haptens are transferred from the endoplasmic reticulum (ER) to an acidic compartm ent of PCs, where they are enzymatically degraded, The processing of t he trifluoroacetylated proteins by this pathway may be a protective me chanism that prevents these covalently altered proteins from inducing an antibody response in most patients who are administered halothane.